Visual interaction with overhauser curves and surfaces

The method of parabolic blending for curve and surface interpolation originally conceived by A. W. Overhauser is applied to the interactive free-form design of three dimensional objects. A significant advantage of the algorithm is the user-oriented control of surface shape that is achieved because one interactively manipulates only coordinates on the design surface, as opposed to parametric slopes or design points.The algorithm is demonstrated using an interactive 3D design system that executes in a dual-minicomputer refresh graphics environment without special 3D hardware. The system provides high level data generation commands and direct visual interaction with structured 3D data using a multi-purpose 3D cursor and shaping tool. Objects composed of points, lines, curves and surfaces of different forms may be interactively created and manipulated.